This invention relates to a method and apparatus for shrinking labels which have been adhered to containers and adhered, by an overlap forming a seam, to itself without requiring rotation of the container as it passes through a linear shrink tunnel. The label in the present invention is formed of a heat shrinkable thermoplastic material having a film side and a foam side with the foam side being positioned against the container about which the label is wrapped.
It has been the practice in the past to use apparatus and methods for providing and shrinking film labels to cylindrical containers by a series of steps such as:
(1) Heat shrink film is first formed into a tube slightly larger in diameter than the container to which it is to be applied;
(2) The container is preheated or, if the film application is carried on in conjunction with the manufacture of glass containers, the glass container can be taken from the manufacturing operation while still warm;
(3) The cylindrical sleeve is placed over the container; and,
(4) The sleeve is then heated to shrink it onto the container.
In those situations where the film is preformed into a cylinder rather than being applied directly from a roll of film material to the container, the procedure is somewhat elaborate and the shrinking of the sleeve is carried out in a long tunnel and the containers are rotated as the shrinkage occurs. A representative patent showing such a method and apparatus is found in U.S. Pat. No. 3,822,459, issued July 9, 1974 to Stephen W. Amberg et al.
Another labeling system for heat shrink labels is disclosed in U.S. Pat. No. 4,416,714, issued to Wolfgang Hoffman and dated Nov. 22, 1983. In this patent there is disclosed a system for applying a precut label to the side of rotating container by securing the leading edge of the label by adhesive to the container and by adhesive being applied between the overlapping leading end and trailing end. The label is of such a width that it projects beyond the junctions of the end portions of the body portion of the container resulting in free standing edges which are then heat shrunk onto the container by heat from an external source. In order for the overlapping surfaces of the label to be formed in a complete adhesive seal, it was necessary to provide a backup member near the heel and near the shoulder of the container when the overlapping ends were pressed together to form a complete vertical seam. Additionally, in the shrinking of such a label, the shrinkage was affected by applying heat to one side of the container, thus necessitating the rotation of the container about its vertical axis as it passes in front of a series of heating zones.
In the present invention, the label has been applied to the container by application of a solvent to the foam surface of a coextruded film-foam sheet of material cut into a label length. The foam with applied solvent is brought into contact with the container. The container is then rotated and a trailing edge of the label is provided with a vertical solvent zone which, when overlapped with the leading edge, forms a vertical and complete seal. The seal, by reason of its being formed from a solvent rather than an adhesive or a heat sensitive hot melt adhesive, becomes instantly tacked to the bottle and, upon overlapping of the trailing and leading edge of the label, firmly adheres to itself to form a strong vertical seam. The bottle thus provided with the wraparound label is carried upright on a conveyor through the heat shrink tunnel and system of the invention.
It is an object of the present invention to provide an apparatus and method for shrinking an applied label of a heat shrinkable plastic which is wrapped around a container without requiring rotation of the container after the label is applied and by linear movement of the labeled container through a shrink tunnel. Again, orientation of the labeled container relative to its seam and movement through the tunnel is not a requirement.
It is a further object of this invention to provide a means for heat shrinking an applied label sleeve about a container in which infrared heat is utilized with the introduction of hot air over the leating elements and with a system of providing more or less heat during the travel of the container through a tunnel.
It is an additional object of this invention to provide a shrink tunnel which is adjustable in width as well as height for accommodating containers of varying sizes and dimensions.
Other objects will be apparent from the following description taken in conjunction with the annexed sheets of drawings.